Hydraulic rod tensioning system

ABSTRACT

A tensioning system for tensioning a stud is provided. The system includes an adapter ring having an external surface, an internal surface engaging the external surface of the stud or puller screw, and at least two bores defined therein. The posts have first and second ends and are disposed in the bores. The first ends are supported by a stop surface, and the second ends extend outwardly from the bores. A cylinder includes an internal surface engaged with the external surface of the adapter ring. First and second pistons are movably positioned within the cylinder with an intermediate cap disposed therebetween to define first and second hydraulic chambers. The first piston is configured for being supported by the second ends of the posts. The hydraulic chambers are hydraulically connected to one another, whereby providing a hydraulic fluid in the chambers operates to apply a tension force on the stud.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/195,455, filed Aug. 1, 2011, now U.S. Pat. No. 9,188,146, whichclaims the benefit of U.S. Patent Application No. 61/371,002, filed Aug.5, 2010. The content of U.S. patent application Ser. No. 13/195,455 and61/371,002 are hereby incorporated by reference in their entirety.

FIELD OF THE INVENTION

The present invention generally relates to a system for tensioning anelongated fastening member, more particularly, to a hydraulic rodtensioning (HRT) system that operates to apply and retain tension to anelongated fastening member, such as, for example, a rod, stud, or bolt.

BACKGROUND OF THE INVENTION

Studs, bolts and rods may be tensioned in order to provide a securemechanical connection between structural members, such as, for example,a pair of opposing flanges on a piece of machinery. The tensioning of astud or bolt is typically accomplished by a tensioning system or devicethat applies an axially-directed force to the stud in a direction awayfrom the structural member. The tensioning system generally includes amechanism for gripping the stud and a load cell. An axially-directedforce is applied by the load cell to the gripping mechanism. Thegripping means transfers the force to the stud, and thereby axiallytensions or stretches the stud. The stud is then mechanically retainedin its stretched or tensioned position by, for example, a nut thatthreadingly engages external threads formed on the stud and which istightened down to engage the flange.

Some conventional tensioning systems utilize mechanical load cells,whereas other tensioning systems use hydraulic load cells. Mechanicalload cells convert mechanical pressure or force to the axial tensioningforce, whereas hydraulic load cells convert hydraulic pressure to theaxial tensioning force. Tensioning systems may be configured as eitherinternal gripping, external gripping or integrated tensioning systemswhere the tensioner is integrated with the fastener.

Consistent with the description provide above, hydraulic tensioningsystems typically include a hydraulic cylinder with a pulling feature,such as a puller nut, that attaches to the stud, and a reacting footthat presses against an exposed surface of the flange. An example of anexisting hydraulic tensioning system can been seen in FIGS. 1A and 1B,which will be described in more detail below. While existing hydraulictensioning systems may be effective in most applications, they sufferfrom a number of drawbacks and deficiencies. For example, existinghydraulic tensioning systems, such as the example provided in FIGS. 1Aand 1B, include a hole or passage having an inner diameter that providesa space along the inner axis to allow the stud to be disposed therein sothat the stud can be engaged with the tensioning system. However, oneresult of including such a hole or passage is a reduction of thehydraulic pressure area for a given tension system diameter. To accountfor this reduction in hydraulic pressure area, either tension load mustbe sacrificed, the tensioning system must be larger in diameter, thetensioning system must be longer to include additional cylinders, or thetensioning system must be designed for higher operating pressures, anyone or combination of which may be undesirable options.

There are also instances in which a hydraulic tensioning systemmalfunctions or breaks when being used to apply an axial tension forceon a stud. Given the high pressures that are used to apply the tensionforce on the stud, a malfunction or breakage of the tensioning systemcould potentially cause one or more of the parts of the tensioningsystem or the stud to be projected toward a user. Currently, there is noadequate mechanism for capturing these broken parts, thereby increasingthe risk of a user being injured in such an event.

As such, there is a need for an improved hydraulic tensioning systemthat overcomes the drawbacks and deficiencies mentioned above. Thepresent invention fulfills these and other needs.

SUMMARY OF THE INVENTION

In order to overcome the above stated problems, the present inventionprovides a tensioning system for tensioning a stud that projects from astructural member, wherein the stud has a central axis. The tensioningsystem may include a puller screw including first and second ends,wherein the first end is configured for selectively engaging the stud,and the second end includes an external surface having external threadsdefined therein. The tensioning system also includes a nut having aninternal surface with threads defined therein and an external surfacewith threads defined therein, the internal surface is configured forengaging the external surface of the puller screw or the externalsurface of the stud if a puller screw is not used, and the nut includesat least two axial bores defined therein. The system further includes atleast two posts, each of the posts have first and second ends and aredisposed in a corresponding one of the at least two axial bores. Each ofthe first ends of the posts are configured for engaging a stop surface,and each of the second ends of the posts are disposed external to the atleast two axial bores and extend axially beyond the second end of thepuller screw in a direction away from the structural member. The systemalso includes a cylinder including an internal surface with threadsdefined therein configured for engaging the external surface of the nut,wherein the cylinder has a bore defined therein. At least one lockingmember is positioned within the bore of the cylinder, and is configuredfor engaging the nut to fixedly position the nut relative to thecylinder. A piston is movably positioned within the cylinder, and isengaged with the second ends of the at least two posts. Further, atleast one spring may be disposed between the nut and the piston.

The present invention may further include a safety guard coupled withthe cylinder and the stud. The safety guard may generally include aguard and a hydraulic interlock assembly. The guard may be coupled withthe stud and the hydraulic interlock assembly, and the hydraulicinterlock assembly may also be coupled with the cylinder to ensure thatthe safety guard is in an acceptable position.

The present invention may further comprise an intermediate cap fixedlypositioned between the piston and the cylinder. The intermediate cap mayinclude a bore defined therein, wherein the piston includes an extensionmember that is coupled with the piston and extends through the bore inthe intermediate cap. As a result, a first hydraulic chamber may bedefined between the piston and the intermediate cap, and a secondhydraulic chamber may be defined between the extension member and thecylinder. Further, a return spring may be disposed between theintermediate cap and the extension member. The extension member may havea passage defined therein that is configured for allowing hydraulicfluid to pass between the first and second hydraulic chambers.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of this invention,and the manner of attaining them, will become apparent and be betterunderstood by reference to the following description of the invention inconjunction with the accompanying drawings, wherein:

FIG. 1A is a front view of a prior art hydraulic tensioning system;

FIG. 1B is a cross-sectional view of the prior art hydraulic tensioningsystem shown in FIG. 1A taken along line 1B-1B;

FIG. 2 is a top view of a HRT system in accordance with the presentinvention;

FIG. 3A is a cross-sectional view of the HRT system shown in FIG. 2taken along line 3-3;

FIG. 3B is a cross-sectional view of an alternative embodiment of theHRT system shown in FIG. 3A showing an female puller screw connected toa stud;

FIG. 3C is a cross-sectional view of an alternative embodiment of theHRT system shown in FIG. 3A showing the integrated nut directly coupledwith a stud;

FIG. 4 is an external tensioned nut (ETN) that may be used inconjunction with the HRT system shown in FIGS. 2, 3B, and 3C;

FIG. 5 is a cross-sectional view of another aspect of the presentinvention wherein the HRT system shown in FIGS. 2 and 3A is being usedin conjunction with a safety guard;

FIG. 6 is an enlarged view of a portion of FIG. 5 showing a hydraulicinterlock assembly coupled to the HRT system; and

FIG. 7 is a cross-sectional view of another embodiment of the HRT systemin accordance with the present invention.

BRIEF DESCRIPTION OF THE INVENTION

With reference to FIGS. 1A and 1B, an exemplary prior art hydraulictensioning system 10 will initially be described so that its featurescan be distinguished from the features set forth in the presentinvention. As best seen in FIGS. 1A and 1B, a stud 12 is being used tofasten a plurality of flanges 14 together using a pair of nuts 16. Inorder to place stud 12 in tension, the nuts 16 are first threadablycoupled to opposing ends of stud 12, and then prior art hydraulictensioning system 10 is coupled to one end of stud 12. Next, a reactionfoot 18 is placed on contact with the outer surface 20 of flange 14,wherein reaction foot 18 is positioned around both stud 12 and nut 16. Acylinder 22 is then placed in contact with a top surface of reactionfoot 18, and a piston 24 is positioned adjacent to and within cylinder22 to form a hydraulic chamber 26 therebetween. A puller nut 28 is thenpositioned within cylinder 22 so that puller nut 28 may be threadablyattached to both the outer surface of stud 12 and the inner surface ofpiston 24.

In order to apply a tension force T to stud 12 in the prior art systemshown in FIGS. 1A and 1B, fluid is introduced from a hydraulic source 30into hydraulic chamber 26 forcing piston 24 to move axially away fromflange 14. Since piston 24 and puller nut 28 are in a fixed relationshipto one another, the axial force of piston 24 is translated throughpuller nut 28. Puller nut 28 subsequently applies the tension force tostud 12 thereby stretching stud 12 in the axial direction away fromflange 14. As puller nut 28 is applying the axial tension force, nut 16is tightened against flange 14 so that the tension force is maintainedin stud 12 after the tensioning system 10 is removed. The prior arttensioning system 10 described above suffers from the drawbacks anddeficiencies described above.

Referring now to FIGS. 2 and 3A, there is shown one embodiment of ahydraulic rod tensioning (HRT) system 32 of the present invention. Withadditional reference to FIG. 5, the HRT system 32 generally operates tocouple a flange 14 a together with, for example, an opposing flange 14 bdisposed on the side of the flange that is opposite the HRT system 32. Astud 12′ extends through a bore 34 a of flange 14 a and through acorresponding bore 34 b in the opposing flange 14 b. It should beunderstood that stud 12′ may have a cross-section of any shape,including, but not limited to, cylindrical, square, trapezoid, etc. Theend of stud 12′ extends from bore 34 b in the opposing flange 14 b andmay be terminated by a nut 16 b that engages the face of flange 14 b.HRT system 32 stretches stud 12′ in an axial direction away from flange14 a and maintains stud 12′ in a tensioned/stretched condition bycoupling stud 12′ to flange 14 a.

In one embodiment of the present invention, stud 12′ has a central axisA, and includes internal threads 36 formed on at least a portion of theaxial length thereof and extending from bore 34 a in flange 14 a,whereby HRT system 32 is configured to engage internal threads 36 ofstud 12′ to apply the tension force. It is also within the scope of thepresent invention to couple HRT system 32″ with the external threads ofa stud 12′ as shown in FIG. 3C to apply a tension force thereto, whichwill be described in more detail below.

As best seen in FIGS. 2 and 3A, HRT system 32 may include a puller screw38, a support foot 40, an integrated nut 42, a tensioner piston 44, anda tensioner cylinder 46. However, it should be understood that HRTsystem 32 need not include puller screw 38.

As best seen in FIG. 3A, support foot 40 has a bore 47 defined thereinconfigured for allowing puller screw 38 to be slidingly disposedtherein, and when puller screw 38 is not utilized, for allowing a studto be slidingly disposed therein. Support foot 40 includes a supportsurface 49 that is adapted to either directly or indirectly engageflange 14 a (FIG. 5). Support foot 40 may be formed entirely, orpartially, of a magnetic material so that the position of support foot40 can be maintained on a sloped flange surface, thereby relieving theoperator from having to hold support foot 40 in place during theinsertion of puller screw 38, when used in the system 32, and during theassembly of the other portion of HRT system 32. It should be understoodthat the configuration of support foot 40 may vary depending on theflange type and is not limited to the configuration shown in FIG. 3A.Support foot 40 may further incorporate additional components, such as,for example, hooks, straps, and alignment features to assist inmaintaining its position on the flange during the assembly and operationof HRT system 32. Further, it should be understood that support foot 40and puller screw 38, when used in the system 32, are separable from theother portions of HRT system 32. The maximum lift weight of HRT system32 is minimized by separating these components allowing them to beinstalled separately.

Puller screw 38 is configured to be slidably positioned within bore 47of support foot 40, and includes first and second ends 48, 50. First end48 is configured to engage HRT system 32 with stud 12′ by itself orthrough the use of an additional fastener. For example, with additionalreference to FIG. 5, first end 48 may be male-tapered and include athreaded feature that is adapted to thread into a female mating featureformed in inner diameter 36 of stud 12′. Puller screw 38 is a versatilecomponent of HRT system 32 in that, instead of directly engaging thestud, puller screw 38 may also be used in conjunction with an additionalfastener to engage the stud. This additional fastener is not necessarilyincluded in HRT system 32 since this additional fastener may take manydifferent forms depending on the type of stud to be engaged by HRTsystem 32. In another aspect, puller screw 38 can easily be removed fromHRT system 32 and replaced with other puller screws with differentconfigurations to accommodate engagement with the stud that will beplaced in tension by HRT system 32. Therefore, HRT system 32 isversatile in that it can be used with different types of puller screwsand/or additional fasteners to engage the HRT system 32 to a given stud.For example, first end 48 of puller screw 38 may also be configured witha female end (not shown but similar to 38′ in FIG. 3B) that is adaptedto engage thread 58 of an external tensioned nut (ETN) 52 (FIG. 4) tocouple HRT system 32 to the stud.

With reference to FIG. 4, ETN 52 includes an outer nut 54 and aretaining ring 56. Outer nut 54 has internal threads 60 configured forengaging corresponding threads on the end of a stud, and externalthreads 58 configured for engaging both internal threads 62 formed inretaining ring 56 and internal threads formed in the female end (notshown) of puller screw 38. The threads 58, 62 on ETN 52 may be buttressthreads, which provide additional capacity for tensioning by keepingmore of the forces parallel to the center line of the stud. Retainingring 56 is used to maintain the position of ETN 52 after HRT system 32stretches the stud by applying a tension force.

As best seen in FIG. 3A, second end 50 of puller screw 38 includes anexternal surface 64 having threads defined therein configured forengaging threads defined in an internal surface 66 of integrated nut 42,wherein nut 42 may be threaded onto puller screw 38. In one embodiment,in order to increase the speed of assembly and disassembly of HRT system32, the threaded connection between puller screw 38 and nut 42 may besegmented so as to produce a bayonet fit such that nut 42 can be freelyslid over puller screw 38 until HRT system 32 is nearly in position,then either puller screw 38 or nut 42 turned only a partial turn toengage the corresponding threads of puller screw 38 and nut 42. Itshould also be understood that the threads on internal surface 66 of nut42 may be adapted to directly engage the end of a stud 12′ of asufficient length, whereby puller screw 38 would not be included in HRTsystem 32.

Integrated nut 42 defines at least two axially-directed bores 68therethrough, wherein bores 68 may be substantially parallel relative tocentral axis A (FIGS. 3A and 5) and may be positioned equidistantrelative to one another about axis A (FIG. 2). Further, nut 42 includesexternal threads 70 formed on its outside surface configured forengaging corresponding internal threads 72 formed in tensioner cylinder46. It should be understood that the threads on internal surface 66 andthe threads on external surface 70 may be buttress threads. One aspectof the invention includes integrating nut 42 with tensioner cylinder 46so that nut 42 becomes part of the tensioning mechanism, as opposed to afastener mechanism.

In the embodiment described, nut 42 includes at least two bores 68 thatreceive a corresponding number of posts 74. However, it is to beunderstood that the present invention can be alternately configured withmore than two bores defined in nut 42, including a corresponding numberof posts disposed in each bore. Also, it should be understood that bores68 may include a cross-sectional shape that matches the cross-sectionalshape of posts 74, for example, but not limited to, a cylindrical,square, trapezoid cross-section.

Each of the posts 74 are received within corresponding bores 68 formedin integrated nut 42. Posts 74 have a first end 76 that is adapted to bedisposed adjacent to and/or in abutting engagement with a stop surface78 of support foot 40. Stop surface 78 of support foot 40 may be a flatsurface formed of a hard material that is capable of withstanding thepressure imposed by posts 74 during the operation of HRT system 32 foreven loading on support foot 40. Each of posts 74 also include a secondend 80 that is disposed outside of bores 68 in a direction T, apredetermined amount outside of bores 68 and beyond nut 42 in asubstantially parallel manner relative to central axis A.

As best seen in FIG. 3A, an alignment plate 82 is shown operablypositioned relative to HRT system 32. Alignment plate 82 may be asubstantially cylindrical member having bottom surface 84 and topsurface 86. Bottom surface 84 is supported by a stepped retainer ring88, wherein a biasing fluid pressure or a biasing member 90, such as,for example, a return spring, may be disposed between nut 42 andtensioner piston 44 that operates to bias retainer ring 88 and topsurface 86 of alignment plate 82 against a bottom surface 92 oftensioner piston 44. If a biasing fluid pressure is utilized, the fluidpressure may be at a pressure level sufficient to return piston (44) toits starting position, but at a low enough pressure to avoid damage tothe HRT system (32). For example, 120 pounds per square inch (psi) plantair pressure may be used as the biasing fluid pressure in HRT system 32.Alignment plate 82 defines a plurality of bores 94 which may extendentirely, or partially, through alignment plate 82 in an axial directionfrom bottom surface 84 toward top surface 86. Posts 74 are received anddisposed within corresponding bores 94, and second end 80 of posts 74engage bottom surface 92 of tensioner piston 44.

Tensioner piston 44 is a substantially cylindrical member that isslidingly disposed within tensioner cylinder 46. Tensioner piston 44includes bottom surface 92, an inner surface 96, and a side/peripheralsurface 98. Peripheral surface 98 defines groove 100 within which isdisposed a sealing member 102, such as, for example, anelastically-deformable O-ring.

Tensioner cylinder 46 is a substantially cylindrical, cup-shaped memberhaving sidewall 104 with an inside surface 104 a, and a closed bottom106 having inside surface 106 a. Inside surface 104 a at the end thereofopposite closed bottom 106 defines internal threads 72 that correspondto and engage external threads 70 of nut 42. Sidewall 104 furtherincludes one or more bores 108 formed therein configured for receiving acorresponding number of locking members 110, for example, lockingscrews. Locking members 110 are threadably positioned in bores 108 andare adapted to engage the outside surface of integrated nut 42 so thatthe tensioner cylinder 46 and integrated nut 42 are locked togetherduring the operation of HRT system 32.

As described above, tensioner piston 44 is disposed within tensionercylinder 46. More particularly, tensioner piston 44 is disposed withintensioner cylinder 46 such that inner surface 96 of piston 44 facesinside surface 106 a of closed bottom 106 of cylinder 46. A hydraulicchamber 112 is defined between inner surface 96 of piston 44 and insidesurface 106 a of closed bottom 106 of cylinder 46, and is peripherallyor radially bounded by a portion of sidewall 104 of cylinder 46. Sealingmember 102 sealingly engages inside surface 104 a, to thereby sealhydraulic chamber 112. Closed bottom 106 defines a hydraulic port 114through which hydraulic fluid is supplied to and/or drawn from hydraulicchamber 112. Thus, cylinder 46 and piston 44 conjunctively define a loadcell of HRT system 32.

In use, the aforementioned component parts of HRT system 32 are operablydisposed in relation to stud 12′, for example, as seen in FIG. 5. Moreparticularly, puller screw 38 is either directly or indirectly engagedwith stud 12′ as previously described, and puller screw 38 is slidablypositioned within bore 47 formed in support foot 40 so that support foot40 is coupled with flange 14 a. With additional reference to FIG. 3A,the threads on internal surface 66 of nut 42 are then engaged with thethreads of external surface 64 on puller screw 38. Next, posts 74 areinserted into bores 68 of nut 42, and first end 76 of posts 74 areplaced against stop surface 78 of support foot 40. One end of returnspring 90 is then placed in contact with an upper surface of nut 42, andretainer ring 88 is placed in contact with the other end of the returnspring 90. Alignment plate 82 is then positioned on top of retainer ring88 so that posts 74 are positioned within bores 94. Thus, alignmentplate 82 aligns and supports posts 74, thereby improving load sharingbetween the posts. Bottom surface 92 of tensioner piston 44 is thenplaced in contact with second end 80 of posts 74. Internal threads 72 oftensioner cylinder 46 are engaged with external threads 70 of nut 42.Once cylinder 46 is in a desired position, locking members 110 aretightened so that they engage the outside surface of integrated nut 42to lock cylinder 46 to integrated nut 42.

A source of hydraulic fluid is then connected to hydraulic port 114, andfluid is thereby provided to hydraulic chamber 112. As hydraulic chamber112 fills with fluid and becomes pressurized, the fluid exerts anaxially directed force that separates piston 44 and cylinder 46. Bottomsurface 92 of piston 44 is placed engagement with posts 74 by thedisplacement of piston 44 under the hydraulic pressure within hydraulicchamber 112. Also, alignment plate 82 is positioned such that topsurface 86 of alignment plate 82 may be placed in contact with piston44. Thus, the axial position of piston 44 relative to flange 14 a isestablished or fixed by the abutting engagement of bottom surface 92 ofpiston 44 with posts 74 which are, in turn, abuttingly engaged withsupport foot 40. As hydraulic chamber 112 is further pressurized,cylinder 46 is displaced in direction T axially away from flange 14 a.As described above, cylinder 46 is fixedly positioned relative tointegrated nut 42, and integrated nut 42 is threadingly engaged withpuller screw 38, and thus the displacement of cylinder 46 is transferredto puller screw 38.

Integrated nut 42 is either directly or indirectly coupled with stud12′, and thus the axial force applied to nut 42 is transferred to stud12′. This force stretches stud 12′ in direction T, and is used totemporarily maintain stud 12′ in its stretched or tensioned condition.As stud 12′ is stretched in direction T, nut 42 and a spanner ring 116(which is attached to nut 16 a via pins 118) are displaced in directionT. While the hydraulic pressure is maintained in chamber 112, spannerring 116 is turned down to thereby bring nut 16 a into abuttingengagement with flange 14 a. The engagement of nut 16 a with flange 14 amaintains stud 12′ in its stretched or tensioned condition when thehydraulic pressure is removed from chamber 112. While the HRT system 32described above utilized hydraulic actuation to impose the tension forcein stud 12′, it should be understood that mechanical actuation is alsowithin the scope of the present invention.

FIG. 3B illustrates an alternative embodiment 32′ of the HRT system,wherein an female puller screw 38′ is used to connect the HRT system 32′to threads formed in an outer surface 37 of a stud 12′. Most of theother components shown in the HRT system 32′ are similar to those shownin system 32 in FIGS. 3A and 5. However, HRT system 32′ may furtherinclude a hardened washer 39 disposed between the support foot 40 andflange 14 a, a stroke indicator 252 which will be described in moredetail below, an anti-rotation screw 41, and a cage retainer 43 disposedbetween cylinder 46 and support foot 40. HRT system 32′ may also beprovided with a female hex-type hydraulic port 114′ that is adapted tobe connected to a male quick connect 166′ for introducing hydraulicfluid into hydraulic chamber 112.

FIG. 3C illustrates yet another embodiment 32″of the HRT system, whereina puller screw is not used, and the stud 12′ is directly connected tothe integrated nut 42. In particular, the threads formed on internalsurface 66 of integrated nut 42 are configured for engaging the threadsformed on the outer surface of an end 51 of stud 12′ to connectintegrated nut 42 with stud 12′. Most of the other components shown inthe HRT system 32″ are similar to those shown in system 32 in FIGS. 3Aand 5. However, HRT system 32″ may further include a support foot 40′that includes an aperture 43 that allows access to a hole 53 defined innut 16 a so that nut 16 a can be tightened during the tensioningprocess. Further, HRT system 32″ may further include a platform 55disposed between the posts 74 and piston 44.

In another embodiment of the present invention, as best seen in FIGS. 5and 6, a safety guard including a guard housing 120 and a quickdisconnect hydraulic interlock assembly 122 may be used in conjunctionwith HRT system 32, or an existing tensioning device, such as hydraulictensioning system 10. The purpose of hydraulic interlock assembly 122 isto conduct hydraulic fluid to the tensioner cylinder 46, provide amechanism to couple and align the guard housing 120 to the tensioningsystem, and prevent hydraulic pressure from being conducted to thetensioner cylinder 46 until guard housing 120 is sufficiently in place.

As best seen in FIG. 5, safety guard housing 120 includes a side wall124 joining two end members 126 a, 126 b, wherein end members 126 a, 126b may be positioned parallel with one another and at a perpendicularangle with respect to side wall 124. Together the side wall 124 and endsmembers 126 a, 126 b surround a substantial portion of HRT system 32, aswell as the stud 12′ and nut 16 a, 16 b assembly, to protect the userfrom being injured in the event that HRT system 32 malfunctions orbreaks. End member 126 a is located adjacent to the end of stud 12′ thatis opposite of tensioning system 32, and a damper block 128 is disposedbetween end member 126 a and stud 12′. Corresponding bores 130, 132 aredefined in end member 126 a and damper block 128, respectively, toaccommodate a locating pin 134 that fastens end member 126 a to the endof stud 12′.

At least a portion of side wall 124 of safety guard housing 120 isdisposed adjacent to side wall 104 of tensioner cylinder 46, and a pairof locating blocks 136 are disposed between side wall 124 and tensionercylinder 46. Corresponding bores (not shown) are defined in side wall124 and locating blocks 136 to accommodate pins 138 that fasten locatingblocks 136 to side wall 124. Blocks 136 are used to properly locate sidewall 124 relative to HRT system 32 by placing blocks 136 in contact withside wall 104 of tensioner cylinder 46.

As best seen in FIGS. 5 and 6, end member 126 b is positioned such thatHRT system 32 is positioned between end member 126 b and stud 12′. Endmember 126 b has a bore defined therein generally configured for havinghydraulic interlock assembly 122 positioned therein. More specifically,an L-shaped ring 142 is positioned in secured engagement with bore 140using a snap ring 144. In addition, a damper block 146 is positionedbetween ring 142 and end member 126 b. Ring 142 includes an innersurface 148 that is threaded for securably engaging hydraulic interlockassembly 122 to safety guard housing 120.

As best seen in FIG. 6, the operation of the quick disconnect hydraulicinterlock assembly 122 produces a clamping action that traps HRT system32, stud 12′ and nuts 16 a, 16 b onto the flanges 14 a, 14 b. Thisserves to contain these components in the event of breakage of stud 12′or internal components of HRT system 32. Hydraulic interlock assembly122 includes a clamping member 150, such as, for example, a clampingscrew or a lever with a cam type clamp, having an outer surface 152 thatis adapted to be threadably engaged with inner surface 148 of bore 140.In particular, clamping member 150 is adapted to be threaded into bore140 until a lower surface 154 abuts a top surface 156 of tensionercylinder 46.

Interlock assembly 122 further includes a stepped axial cavity 160defined therein that is configured for housing a female hydraulicconnector 162 and a disconnect bias spring 164. Female hydraulicconnector 162 mounted to guard housing 120 via hydraulic interlockassembly 122, and is adapted to receive a male connector 166 mounted onHRT system 32 to convey hydraulic fluid from a hydraulic source via ahydraulic disconnect 168, such as, for example, a hydraulic quickdisconnect. Female hydraulic connector 162 may include locking balls anda collar 170 that is adapted to be slidingly disposed within cavity 160.One end 172 of disconnect bias spring 164 is disposed against a ledge174 defined in cavity 160, and the other end 176 is attached to acoupling member 178 to bias coupling member 178 away from HRT system 32.Coupling member 178 is rigidly connected to female hydraulic connector162 and acts as a hydraulic conduit, a hydraulic adapter and a physicalextension to female hydraulic connector 162. A passage 180 allows thehydraulic fluid to be conveyed from the hydraulic source to hydraulicchamber 112 in cylinder 46. Further, clamping member 150 includes aninterlock shoulder 182 that prevents sliding collar 170 from fallinginto position until clamping member 150 is in proper position. Shoulder182 provides an important added condition that lower surface 154 and topsurface 156 must be in contact before the hydraulic connection can becompleted. In the event that the user fails to completely clamp theguard housing 120, the hydraulic pressure will be held in interlockassembly 122 and HRT system 32 will not work, thus providing a safetyfunction. Further, spring loaded pins 158 may be disposed withinclamping member 150 to prevent female hydraulic connector 162 frommoving into a connectable position with male connector 166 untilsufficient clamping force is generated on clamping member 150. Further,a ring 183 is fixed to male connector 166 adjacent to shoulder 182 toprevent the inadvertent connection of an unmodified female hydraulicconnector 162 by preventing sliding collar 170 from sliding into place,wherein the face of female hydraulic connector 162 is machined toaccommodate ring 183.

When using the safety guard housing 120 and the hydraulic interlockassembly 122 shown in FIGS. 5 and 6, the user would first position thestud 12′ and nuts 16 a, 16 b on respective flanges 14 a, 14 b handtight. Spanner ring 116 is fitted to the nut 16 a, and then puller screw38 is threaded into the end of stud 12′ until tight. Next, support foot40 is then slid over puller screw 38 and positioned to properly matewith a face of flange 14 a. The remainder of the components of HRTsystem 32 are then threaded onto puller screw 38 as described above.Safety guard housing 120 is fitted over flanges 14 a, 14 b, stud 12′,nuts 16 a, 16 b, and HRT system 32. The locating pin 134 is fitted intothe back side of stud 12′, and the female hydraulic connector 162 isaligned with the male connector 166. Clamping member 150 is threadedinto ring 142 until sliding collar 170 on female hydraulic connector 162snaps down and locks with male connector 166. Now that HRT system 32 isclamped tight on flanges 14 a, 14 b and the hydraulic connection iscomplete, the user may allow hydraulic fluid to pass from a hydraulicsource, and through passage 180 in hydraulic interlock assembly 122 andtensioning cylinder 46, so that HRT system 32 stretches stud 12′, aspreviously described above with respect to HRT system 32. To retain thetension load placed on stud 12′, spanner ring 116 is turned so that nut16 a is in abutting engagement with flange 14 a. Pressure may then bereleased from HRT system 32, and return spring 90 reset the position oftensioner piston 44 and posts 74. The user then turns clamping member150 to loosen guard housing 120, and pulls collar 170 through couplingmember 178 causing female hydraulic connector 162 to disengage from maleconnector 166, and thereby releasing the hydraulic lock. The safetyguard housing 120 may now be lifted and removed from HRT system 32.

Another embodiment of a HRT system is shown in FIG. 7 and is identifiedwith reference numeral 200. HRT system 200 is a two-stage device andgenerally includes a cage platform 202, an adapter ring 204, a tensionercylinder 206, a lower tensioner piston 208, and an upper tensionerpiston 210. It should be understood that adapter ring 204 is similar tointegrated nut 42 as previously described.

Cage platform 202 includes a lower surface 212 that is adapted to eitherdirectly or indirectly contact a flange, such as, for example, flange 14a (FIG. 5). Cage platform 202 has a bore 214 defined therein configuredto allow a stud or puller screw (not shown) to pass therethrough.Further, cage platform 202 may include two or more bores 216 adapted toallow first ends 217 of a corresponding number of posts 218 to bepositioned therein.

Adapter ring 204 includes internal and external threads 220, 222, aswell as bores 224 adapted to allow posts 218 to be positioned therein.Internal threads 220 are configured to allow for engagement with eithera stud or a puller screw. It should be understood that internal threads220 formed in adapter ring 204 may be adapted to directly engage the endof a stud of a sufficient length, whereby a puller screw would not beincluded in HRT system 200. External threads 222 are configured to allowengagement with tensioner cylinder 206 so that stud, adapter ring 204and tensioner cylinder 206 are all fixedly positioned relative to oneanother during the operation of HRT system 200. Tensioner cylinder 206further includes a hydraulic port 226.

Lower tensioner piston 208 includes a lower surface 228 and an uppersurface 230. Lower surface 228 is in contact with a first return spring232 and may be placed in abutting engagement with second ends 234 ofposts 218. Further, upper tensioner piston 210 is fixedly positionedrelative to lower tensioner piston 208 and extends upwardly from uppersurface 230 of lower tensioner piston 208. Upper tensioner piston 210includes a top wall 236 that is generally parallel with lower tensionerpiston 208, and a downwardly extending leg member 238 that connects topwall 236 to lower tensioner piston 208. An intermediate cap 240 isfixedly coupled with tensioner cylinder 206 and is positioned betweentop wall 236 and lower tensioner piston 208. Intermediate cap 240 has abore 242 formed therein configured to allow leg member 238 to extendtherethrough. In addition, a second return spring 244 is positionedbetween intermediate cap 240 and top wall 236.

Two separate hydraulic chambers 246 a, 246 b are provided in HRT system200. The first hydraulic chamber 246 a is formed between lower tensionerpiston 208 and intermediate cap 240, and the second hydraulic chamber246 b is formed between intermediate cap 240 and tensioner cylinder 206.Seals 248 (e.g., German “fit”) may be positioned between intermediatecap 240 and leg member 238 of upper tensioner piston 210, betweentensioner cylinder 206 and top wall 236 of upper tensioner piston 206,and between tensioner cylinder 206 and lower tensioner piston 208. Acentral port 250 may be formed in leg member 238 to allow for hydraulicfluid to be passed between hydraulic chambers 246 a, 246 b. In thisparticular embodiment, hydraulic pressure is conveyed through centralport 250 that connects hydraulic chambers 246 a, 246 b which results innearly twice the amount of force produced for a given pressure level. Itshould be understood that this concept should not be limited to the useof just two hydraulic chambers 246 a, 246 b, as the use of more than twohydraulic chambers is also contemplated and within the scope of thepresent invention. As would be understood by one skilled in the art, thefundamental operation of the HRT system 200 is substantially the same aswas described with respect to the HRT system 32, therefore the operationof HRT system 200 will not be described an any additional detail.

HRT system 200 may further include a stroke indicator 252 which may beused to inform the user of the amount of stroke capacity that is beingutilized during a tensioning cycle. Stroke indicator 252 may include atleast one pin 254 mounted to and extending from tensioner cylinder 206.Pin 254 passes through an elongated slot formed in cage platform 202,wherein the outer surface of cage platform 202 has indicia indicatingwhether the HRT system 200 is in an extended position (E) or a retractedposition (R). In addition, pin 254 operates to ensure that cage platform202 and tensioner cylinder 206 are kept moveably attached to oneanother. Further, pin 254 may also extend into adapter ring 204 so thatpin 254 not only operates as an indicator, but also a locking mechanismthat fixedly positions cage platform 202 and adapter ring 204. However,it should be understood that pin 254 need not extend into adapter ring204, in which case a separate locking mechanism, for example, one ormore locking members 110 (FIG. 3A), would be used to fixedly positioncage platform 202 to adapter ring 204.

From the foregoing, it will be seen that this invention is one welladapted to attain all the ends and objects hereinabove set forthtogether with other advantages which are obvious and which are inherentto the method and apparatus. It will be understood that certain featuresand sub-combinations are of utility and may be employed withoutreference to other features and sub-combinations. This aspect iscontemplated by and is within the scope of the claims. Since manypossible embodiments of the invention may be made without departing fromthe scope thereof, it is also to be understood that all matters hereinset forth or shown in the accompanying drawings are to be interpreted asillustrative and not limiting.

The constructions described above and illustrated in the drawings arepresented by way of example only and are not intended to limit theconcepts and principles of the present invention. As used herein, theterms “having” and/or “including” and other terms of inclusion are termsindicative of inclusion rather than requirement.

While the invention has been described with reference to preferredembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof to adapt to particular situations without departingfrom the scope of the invention. Therefore, it is intended that theinvention not be limited to the particular embodiments disclosed as thebest mode contemplated for carrying out this invention, but that theinvention will include all embodiments falling within the scope andspirit of the appended claims.

What is claimed is:
 1. A tensioning system for tensioning a stud thatprojects from a structural member, the stud having a central axis, thetensioning system comprising: an adapter ring including internal andexternal surfaces, the internal surface is configured for engaging thestud, the adapter ring further including at least two axial boresdefined therein; at least two posts, each of the posts having first andsecond ends, each of the posts disposed in a corresponding one of the atleast two axial bores defined the adapter ring, each of the first endsof the posts configured for being supported by the structural member,wherein a portion each of the second ends of the at least two postsextend outwardly from the at least two axial bores of the adapter ringin a direction away from the structural member; a cylinder including asidewall and a closed bottom, the sidewall including an internal surfaceconfigured for engaging the external surface of the adapter ring tofixedly position the adapter ring to the cylinder; a first pistonmovably positioned within the cylinder, the first piston configured forbeing supported by the second ends of the at least two posts; a secondpiston movably positioned within the cylinder; a leg member coupled tothe first piston and the second piston; an intermediate cap fixedlycoupled with cylinder and including an aperture defined thereinconfigured to allow the leg member to be movably positioned therein,wherein the intermediate cap is disposed between the first piston andthe second piston thereby defining a first hydraulic chamber between thefirst piston and the intermediate cap, wherein a second hydraulicchamber is defined between the second piston and the cylinder, whereinwhen a hydraulic fluid is fed into the first hydraulic chamber and thesecond hydraulic chamber, the first and second pistons move away fromthe cylinder to apply a tension force on the stud.
 2. The tensioningsystem in accordance with claim 1, wherein the leg member is fixedlycoupled to the first piston and the second piston.
 3. The tensioningsystem in accordance with claim 1, wherein the first and second pistonsare spaced apart and fixedly positioned relative to each other.
 4. Thetensioning system in accordance with claim 1, wherein the leg memberincludes a central hydraulic port for placing the first and secondhydraulic chambers in fluid communication.
 5. The tensioning system inaccordance with claim 4, wherein the cylinder includes a hydraulic portfor allowing input of the hydraulic fluid into the first hydraulicchamber and into the second hydraulic chamber through the centralhydraulic port.
 6. The tensioning system in accordance with claim 1,further comprising a first biasing member disposed between the adapterring and the first piston.
 7. The tensioning system in accordance withclaim 6, further comprising a second biasing member disposed between theintermediate cap and the second piston.
 8. The tensioning system inaccordance with claim 1, further comprising a second biasing memberdisposed between the intermediate cap and the second piston.
 9. Thetensioning system in accordance with claim 1, further comprising a cageplatform positioned between the at least two posts and the structuralmember.
 10. The tensioning system in accordance with claim 9, whereinthe cage platform includes a first bore defined therein configured forreceiving the stud, wherein the cage platform further includes at leasttwo second bores, wherein each of the at least two second bores areconfigured for receiving a corresponding one of the at least two posts.11. The tensioning system in accordance with claim 9, further comprisinga pin fixedly coupled with the cylinder and extending through anelongated slot formed in the cage platform.
 12. The tensioning system inaccordance with claim 11, wherein a surface of the cage platform hasindicia indicating the position of the cylinder relative to the cageplatform.
 13. The tensioning system in accordance with claim 1, whereinthe at least two axial bores defined in the adapter nut aresubstantially parallel relative to the central axis.
 14. The tensioningsystem in accordance with claim 1, wherein the at least two axial boresdefined in the adapter nut are positioned equidistant relative to oneanother about the central axis.
 15. A tensioning system for tensioning astud that projects from a structural member, the stud having a centralaxis, the tensioning system comprising: an adapter ring includinginternal and external surfaces, adapter ring including at least twoaxial bores defined therein; a puller screw including first and secondends, the first end of the puller screw configured for engaging thestud, the second end of the puller screw configured for engaging theinternal surface of the adapter ring; at least two posts, each of theposts having first and second ends, each of the posts disposed in acorresponding one of the at least two axial bores defined the adapterring, each of the first ends of the posts configured for being supportedby the structural member, wherein a portion each of the second ends ofthe at least two posts extend outwardly from the at least two axialbores of the adapter ring in a direction away from the structuralmember; a cylinder including a sidewall and a closed bottom, thesidewall including an internal surface configured for engaging theexternal surface of the adapter ring to fixedly position the adapterring to the cylinder; a first piston movably positioned within thecylinder, the first piston configured for being supported by the secondends of the at least two posts; a second piston movably positionedwithin the cylinder; a leg member coupled to the first piston and thesecond piston; an intermediate cap fixedly coupled with cylinder andincluding an aperture defined therein configured to allow the leg memberto be movably positioned therein, wherein the intermediate cap isdisposed between the first piston and the second piston thereby defininga first hydraulic chamber between the first piston and the intermediatecap, wherein a second hydraulic chamber is defined between the secondpiston and the cylinder, wherein when a hydraulic fluid is fed into thefirst hydraulic chamber and the second hydraulic chamber, the first andsecond pistons move away from the cylinder to apply a tension force onthe stud.
 16. The tensioning system in accordance with claim 15, whereinthe leg member is fixedly coupled to the first piston and the secondpiston.
 17. The tensioning system in accordance with claim 15, whereinthe first and second pistons are spaced apart and fixedly positionedrelative to each other.
 18. The tensioning system in accordance withclaim 15, wherein the leg member includes a central hydraulic port forplacing the first and second hydraulic chambers in fluid communication.19. The tensioning system in accordance with claim 18, wherein thecylinder includes a hydraulic port for allowing input of the hydraulicfluid into the first hydraulic chamber and into the second hydraulicchamber through the central hydraulic port.
 20. The tensioning system inaccordance with claim 15, further comprising a first biasing memberdisposed between the adapter ring and the first piston.
 21. Thetensioning system in accordance with claim 20, further comprising asecond biasing member disposed between the intermediate cap and thesecond piston.
 22. The tensioning system in accordance with claim 15,further comprising a second biasing member disposed between theintermediate cap and the second piston.
 23. The tensioning system inaccordance with claim 15, further comprising a cage platform positionedbetween the at least two posts and the structural member.
 24. Thetensioning system in accordance with claim 23, wherein the cage platformincludes a first bore defined therein configured for receiving thepuller screw, wherein the cage platform further includes at least twosecond bores, wherein each of the at least two second bores areconfigured for receiving a corresponding one of the at least two posts.25. The tensioning system in accordance with claim 23, furthercomprising a pin fixedly coupled with the cylinder and extending throughan elongated slot formed in the cage platform.
 26. The tensioning systemin accordance with claim 25, wherein a surface of the cage platform hasindicia indicating the position of the cylinder relative to the cageplatform.
 27. The tensioning system in accordance with claim 15, whereinthe at least two axial bores defined in the adapter nut aresubstantially parallel relative to the central axis.
 28. The tensioningsystem in accordance with claim 15, wherein the at least two axial boresdefined in the adapter nut are positioned equidistant relative to oneanother about the central axis.